1. Field of Invention
The present invention relates to a driving method for an electro-optical apparatus that can provide a high-quality gradation display, a driving circuit therefor, an electro-optical apparatus, and electronic equipment.
2. Description of Related Art
Generally, an electro-optical apparatus performs display by utilizing an electro-optical change of an electro-optical material. A liquid crystal display unit employing liquid crystal as an electro-optical material, which is an alternative to a cathode ray tube (CRT), is widely used as a display portion of a display device in various types of information processing equipment.
A conventional liquid crystal display device has the following configuration. Specifically, the conventional liquid crystal display device includes a device substrate, on which pixel electrodes arranged in a matrix-like manner and switching devices connected to the pixel electrodes are provided, an opposing substrate on which counter electrodes respectively facing the pixel electrodes are formed, and liquid crystal serving as the electro-optical material sandwiched between these substrates.
Further, when a scanning signal is applied to one of the switching devices through a scanning line, this switching device is placed into a conducting state. When a voltage signal, corresponding to a gradation level, is applied to one of the pixel electrodes through a data line when the switching device is in the conducting state, electric charge, corresponding to the voltage signal, is stored between this pixel electrode and a corresponding one of the counter electrodes. Then, after the electric charge is stored therein, the storage of the electric charge in this liquid crystal layer is maintained due to the capacitive property and storage capacity of the liquid crystal layer, even when this switching device is placed into an off-state. In the case that each of the switching devices is driven in this manner, and the amount of the stored charge is controlled according to gradation levels, the orientation state of liquid crystal molecules changes. Thus, density levels vary with pixels. This enables the gradation display.
However, voltage signals applied to the data lines correspond to gradation levels and are analog signals. Thus, display unevenness is liable to occur due to nonuniformity of various device characteristics and wiring resistance.
An area gradation method is known wherein gradation levels are realized by dividing one pixel into a plurality of sub-pixels, and changing the on-state or off-state of each of the sub-pixels. In the case of the area gradation method, gradation levels are realized by only turning on or off the sub-pixels, so that it is sufficient to use binary voltage signals to be applied to the data lines. Consequently, it is unlikely that the display unevenness due to the nonuniformity of various device characteristics and wiring resistance will occur. However, according to this area gradation method, when the number of division of one pixel into sub-pixels is k, the number of gradation levels is 2k, and multi-level gradation display using gradation levels, the number of which is more than 2k, cannot be realized.